300 Experimental Zoology 
similar kind gave the same result. Especially instructive is 
the case where the new ectoderm is derived partly from one 
component, partly from the other species (as when the tail is 
cut off as shown at 0-b in Fig. C). No influence of the ecto- 
E 
Fic. 22. Grafted tail of frog. Fig. A, Rana sylvatica with grafted tail of 
Rana palustris. Fig. B, reciprocal graft. Fig. C, late stage of last. Fig. D, 
newly regenerated tail of Fig. A cut off at a-a. Fig. E, newly regenerated tail of 
Fig. C cut off at a-a. 
derm cells on each other could be detected, although they are 
in intimate contact. 
The attempt to unite pieces of brown hydra, H. fusca, to 
pieces of green hydra, H. viridis, has not succeeded. Wetzel 
has shown that although the two pieces will stick together for 
a few hours, or even days, they subsequently separate; but the 
union of Hydra fusca and H. grisca was successfully carried out. 
